CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Preferred stock, par value (usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (shares)	20,000,000us-gaap_PreferredStockSharesAuthorized	20,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, shares outstanding (shares)	7,251,515us-gaap_PreferredStockSharesOutstanding	7,251,515us-gaap_PreferredStockSharesOutstanding
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common Stock, Shares Authorized	1,000,000,000us-gaap_CommonStockSharesAuthorized	1,000,000,000us-gaap_CommonStockSharesAuthorized
Common Stock, Shares, Issued	665,109,487us-gaap_CommonStockSharesIssued	664,944,232us-gaap_CommonStockSharesIssued
Treasury stock, shares	1,585,667us-gaap_TreasuryStockShares	1,614,312us-gaap_TreasuryStockShares
Cash and cash equivalents	$ 2,907	$ 4,108
Short-term derivative assets ($12 and $16 attributable to our VIE)	612us-gaap_DerivativeAssetsCurrent	879us-gaap_DerivativeAssetsCurrent
Proved oil and natural gas properties ($488 and $488 attributable to our VIE)	60,769	58,594
Less: accumulated depreciation, depletion and amortization (($318) and ($251) attributable to our VIE)	(44,700)	(39,043)
Other current liabilities ($12 and $15 attributable to our VIE)	2,474us-gaap_OtherLiabilitiesCurrent	3,061us-gaap_OtherLiabilitiesCurrent
Variable Interest Entities, Primary Beneficiary [Member]
Cash and cash equivalents	1	1
Short-term derivative assets ($12 and $16 attributable to our VIE)	12	16
Proved oil and natural gas properties ($488 and $488 attributable to our VIE)	488	488
Less: accumulated depreciation, depletion and amortization (($318) and ($251) attributable to our VIE)	(318)	(251)
Other current liabilities ($12 and $15 attributable to our VIE)	$ 12	$ 15

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Capitalized costs of proved properties incurred for any combination mineral interests acquisitions; wells and related equipment; support equipment and facilities; and uncompleted wells and equipment and other costs not previously disclosed within this table.

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